What is a copy constructor ?

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Accepted Answer

The correct option is (2):
A copy constructor is a special type of constructor in Object-Oriented Programming, particularly in languages like C++, that is specifically designed to create a new object as an *exact copy* of an already existing object of the same class. Its fundamental role is to perform initialization, meaning it sets the initial state of the *newly created* object by copying the data member values from a source object. This constructor is automatically invoked in key situations, such as when an object is passed by value to a function, when an object is returned by value from a function, or when an object is explicitly initialized with another object of the same type. It ensures that the process of duplicating an object is handled correctly, including the necessary deep copy operations for any dynamically allocated memory within the class.

The incorrect option is (1):
A constructor that allows a user to move data from one object to another is technically known as a **move constructor**, not a copy constructor. Move constructors are a C++11 feature designed for optimization, and their purpose is to *transfer* resources from a temporary source object to a new object, leaving the source in a valid but empty state. This process avoids the expensive duplication of data, which is distinct from the memory allocation and value-by-value copying done by a copy constructor.

The incorrect option is (3):
The constructor's role is to construct and initialize an object, not to perform comparisons. The functionality to check whether two objects are equal is typically implemented by overloading the **equality operator (`==`)** or by writing a separate, explicit comparison member function, such as an `equals()` method. A constructor operates on the object being created, and it is not intended to return a Boolean result based on the comparison of two existing objects.

The incorrect option is (4):
The primary responsibility for deleting an object or cleaning up its resources is handled by the **destructor**, not a constructor. The destructor is automatically called when an object's lifetime ends, ensuring that any dynamically allocated memory is properly deallocated to prevent memory leaks. Constructors are only concerned with the creation phase of an object, which is the opposite of deletion.